1. Field of the Invention
The present invention is related generally to combined fluid flow and particle motivating force methods for particle manipulation, and is related specifically to dynamic equilibrium separation, concentration, dispersion and mixing apparatus and methods.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Dielectric particles suspended in a dielectric media are polarized under the action of electric fields. If the field is spatially inhomogeneous, it exerts a net force on the polarized particle known as a dielectrophoretic (DEP) force [1]. This force depends upon the temporal frequency and spatial configuration of the field as well as on the dielectric properties of both the medium and the particles.
Dielectrophoresis is an increasingly popular method to separate particles in microflows [2]. DEP forces can be switched on and off to selectively capture cells, bacteria, spores, DNA, proteins, and other matter. The art has envisioned, for instance, an application using DEP to capture a suspected pathogen which then is shuttled to a selected area of the microfluidic device where its DNA is extracted and analyzed.
Since the dielectrophoretic mobility of a particle scales directly with its surface area the manipulation of smaller particles requires larger gradients of the electric fields. Nevertheless, by using microfabricated electrodes to generate large electric field gradients, it is known in the art to move submicron particles by means of DEP [3, 11].
However, large electric field gradients may strongly interact with the background media creating, by several electro-hydrodynamic effects, flows whose drag perturbs the particle trajectories. An understanding of this disturbance remains crucial to predict and control it in developing applications of DEP to specific microfluidic devices. On the other hand, the combined dynamics induced by both advection and electric forces remains a largely unexplored but interesting field of research.
It can be seen, then that there is a need in the art for improved methods of and apparatuses for efficiently and accurately detecting, separating, mixing, and harvesting of small amounts of particles (e.g., atoms, molecules, cells in biological and chemical assays) using combined fluid flow and dielectrophoresis methods for particle manipulation. The present invention satisfies this need and that of a more general case when the particle motivating force is not dielectrophoretic in nature.